制冷系统用两级先导式电磁阀动力学特性的仿真与实验

对制冷系统用两级先导式电磁阀动力学特性进行数值仿真与实验.建立了基于电磁阀阀芯振动与制冷剂流动相耦合的动力学模型,模型充分考虑阀芯振动,阀内各腔压力变化,阀前后管路内压力渡传递,得到了实验结果的验证.获得电磁阀在不同工作条件下的动态响应与工作状态,讨论了闽前管路内压力波对电磁阀自激振动与压力脉动的影响.     

果粒饮料盒中袋灌装阀阀道结构分析与优化

目的为了确定盒中袋灌装阀阀道结构以及阀芯下降高度,对盒中袋灌装阀进行流体流场仿真计算。方法运用Fluent软件对盒中袋灌装机的灌装阀阀道结构进行流场分析,根据流速场以及压力场的分布,找出应力集中区域,进行了结构优化;再运用Fluent软件对阀芯下降不同高度数值后,进行模拟仿真,根据阀芯下降不同高度时流速场与压力场的变化,找出最佳高度。结果得到了优化的结构工艺参数以及合适的阀芯下降高度。结论阀型拐角θ1和θ2为30°,阀芯下降高度为3 mm时,物料在阀道中的流动状态最合适。     

电液谐振式高频疲劳试验台动态特性研究

针对由单出杆液压缸与二位三通2D阀组成的电液谐振式高频疲劳试验台,因单出杆液压缸无杆腔与2D阀相连,有杆腔恒通油源。而2D阀突破常规电液伺服阀频宽极限,具有宽频带、高频响等特点,通过改变阀芯旋转速度及阀口轴向开度,可对系统分别进行变频、变幅控制。对采用2D阀控制技术的电液谐振式高频疲劳试验台建立数学、仿真模型,并对该试验台谐振工况进行仿真与实验研究,结果表明该系统谐振工况输出位移（载荷力）与激振力大,消耗外界功率低。     

液压滑阀阀芯结构对流场的影响

目的滑阀结构对阀流场有直接影响,为提高滑阀性能,对不同阀芯结构阀流场进行分析。方法采用U型、三角型和无节流槽3种阀芯结构,利用ADINA软件流固耦合模块,对3种阀芯的滑阀流场情况进行分析计算,研究阀流道内流体流速和压力分布情况。结果在进口处具有较高的流速,无节流槽阀芯在阀口处速度降低最大,U型节流槽阀芯在阀口处速度降低最小;U型节流槽阀芯在整个流道内压力变化较小,无节流槽阀芯在整个流道内压力变化最大。结论阀芯开设节流槽可以明显改善阀流道内流场分布情况,改善阀的性能,其中U型节流槽阀芯具有良好的性能。     

一种锥形节流阀工作过程流-固耦合动力学响应的影响因素分析

基于三维流-固耦合有限元动力学仿真分析模型和直接耦合算法,分析了一种锥形节流阀在入口流速脉冲激励下由关闭状态开启而后重新关闭全过程的流量特性、压差特性及阀门开度的高频波动等非线性动力学响应特性,并采用小波分析方法等对阀门开度响应等进行了时-频域分析。选择不同的流体-结构模型的数值积分方法组合及时间步长对流-固耦合动力学求解算法进行了实际应用检验;然后对阀芯质量、弹簧参数与油液参数等系统参数以及激励速度幅值与脉宽等激励参数对其工作过程动力学响应的影响进行了细致的数值分析比较。结果表明:流体模型积分算法的选择对流-固耦合计算结果的影响较大;对该阀而言,阀芯质量与油液体积弹性模量的改变对阀芯振动频率的影响较为显著,油液粘度的改变对阀门开启的滞后量及振动相位的影响较大,而弹簧刚度及预紧力的改变对阀门的最大稳定开度的影响较大;阀芯与阀座间的碰撞使阀芯的振动频率提高。     

新型先导式压力开关阀的研究及应用

该文通过对先导式溢流阀的工作原理进行分析,根据先导式溢流阀的工作特点,以先导式溢流阀为原型,将被动式控制改为主动式控制,变形出一种主动控制的新型先导式压力开关阀,将新型先导式压力开关阀的工作步骤进行分解分析,利用液压原理和力学公式进行推导,总结新型先导式压力开关阀的3个特点,从新型先导式压力开关阀的特点入手,针对传统卫浴市场阀门操作不够简单,使用不够轻便的问题,结合电器按钮的方式创造出不同于常规操作方式的新型阀芯。     

给水三通阀阀杆断裂失效分析

通过对发生断裂失效的给水三通阀阀杆进行宏观检查、化学成分分析、拉伸试验、冲击试验、金相检验和硬度试验,分析了其断裂原因。结果表明:阀杆断裂为疲劳断裂,阀杆断裂的主要原因是表面渗氮处理增加了阀杆与阀芯表面相交处的脆性,加上阀杆与阀芯表面相交的位置结构突变造成应力集中,在流体的长期挤压和剪切力作用下,便会在应力集中部位的渗氮层中形成裂纹源,并在阀杆服役时的交变应力的作用下,裂纹从渗氮层逐步扩展到阀杆基体,最终导致阀杆断裂失效。     

柴油机进气阀开裂原因分析

某中速柴油机进气阀装机使用3567h后发生开裂.采用化学分析、金相检验及扫描电镜断口分析等手段对进气阀开裂原因进行了分析.结果表明,进气阀开裂位于阀头应力最大处.进气阀的阀头上部开裂为工作中存在温度梯度导致的热胀冷缩及交变应力产生的热疲劳所致;阀头底部开裂为腐蚀疲劳所致.     

二通插装阀方向元件的动作响应特性研究

针对某造型机中二通插装阀方向元件的启闭特性,建立数学模型理论,分析插装阀阀芯动作特性的影响因素;利用AMESim建立二通插装阀模型,通过仿真分析弹簧刚度与预压缩力、阀芯面积比与油液通流方向、阻尼孔通径与安装位置等因素对阀芯动作特性的影响。由仿真结果可知:与弹簧预压缩力相比,阀芯的弹簧刚度对响应特性影响较大;油液在插装阀中通流方向以及插装阀A和X腔的面积比对阀芯动作特性有明显影响;阻尼孔的通径和安装位置对阀芯动作特性均有较大影响,实际工程中选定阻尼孔的通径和安装位置时应综合考虑系统工作周期和冲击性要求。     

高速公路防撞垫概念模型的优化及控制参数研究

为了更有效的对高速公路防撞垫进行设计,了解碰撞过程中车辆的运动形式和防撞垫的力学性能。该文使用三自由度弹簧质量系统对现有的概念模型进行优化,并使用显式动力学软件LS-DYNA对该系统进行数值模拟。最终得出重为1.3 t的汽车以60 km/h的速度正面撞击防撞垫工况下,影响乘员安全的控制参数为防撞垫概念模型的屈服荷载、屈服前刚度和压缩距离。     

Fracture of aluminium foam core sacrificial cladding subjected to air-blast loading

The effect of core density and cover plate thickness on the blast response of sacrificial cladding panels has been investigated through blast loading experiments and finite element modelling on structures with steel cover plates and aluminium foam cores. A range of foam core densities were examined, with 10%, 15% and 20% nominal relative densities. The cover plate thickness greatly influenced the response of the sacrificial cladding. Cover plates that were 2 mm thick exhibited significant permanent deformations and variable percentage crush across the section, whereas the 4 mm thick cover plates were more rigid causing the core to compress uniformly. Considerable fracture of the foam was observed after blast testing, particularly for the lower density foams. The effect of bonding the cover plate to the core was also examined. Numerical simulations of the experiments were performed using ABAQUS/Explicit to provide insight into the response mechanism. It was shown through the finite element simulations that tensile fracture of the foam occurred during the unloading phase of response and that adhesion of the cover plate to the foam caused higher levels of cracking. This was consistent with the experimental observations.     

Analytical model for laminated-glass plate

This paper presents an analytical model of laminated-glass plate (two external glass plies and a polymeric interlayer). Mechanical behavior is described by a system of three exact and explicit equations. The equations are solved for the simply-supported rectangular plate, under lateral uniformly distributed static loading. However, the solution for other restraints, shapes, and loads can be obtained without altering the model, but simply by adjusting the mathematical form of the functions which the equations are solved by.The model represents a tool for design and assessment. Since it is exact, the model allows for the checking and refining of finite element models and semi-empirical formulas. Since it is both analytical and explicit, the model allows one to gain a better understanding of the mechanical behavior of laminated glass plate.The model can also be applied to laminated plates in general, i.e., sandwich structures (thick skin sandwiched by thin core, as well as thin skin sandwiched by thick core provided that this thick core is relatively soft).     

顶盖内板拉深工艺分析及模具设计

根据顶盖内板的结构特点,分析了零件的冲压工艺性,确定了成形步骤.为获得成形质量良好的零件,以有限元模拟软件Autoform为平台,对零件的拉深成形过程进行了模拟.以模拟结果为依据,指导并详细介绍了各个工序模具的设计要求和整体结构.生产试验表明:有限元模拟结果准确度高,模具设计合理,结构可靠,能保证零件的成形质量,满足批...     

基于抗振动疲劳的薄板加筋设计分析

振动是航空薄板常见的载荷形式,通常采用加强筋来减小振动幅度,从而提高薄板寿命.研究薄板的抗振动疲劳加筋方法,探讨加强筋与板的连接方式以及加强筋的布置方向对薄板振动与疲劳的影响机制.首先,基于振动理论和板筋变形协调条件,建立加筋薄板的运动方程.然后,建立铆接、点焊和滚焊连接形式的加筋薄板有限元模型,探讨连接单元的动力学建模方法;在此基础上,研究连接形式和加筋安装方向对薄板结构动力学特性的影响;最后,结合动力响应分析探讨板筋连接方式和加筋安装方向对疲劳寿命的影响.研究结果表明,双向加筋薄板在低频振动时刚度高于单向加筋薄板,双向加筋有利于提高结构抗疲劳强度,铆接单向加筋薄板的振动疲劳寿命最短.     

Stochastic fatigue damage assessment of metro switch blade

Stochastic fatigue damage of a metro switch blade is studied with a combination of explicit finite element model (FEM), multiaxial fatigue criterion, and statistical analysis. The explicit FEM is used to reproduce dynamic procedure and to provide detailed stress/strain state variation. A multiaxial fatigue criterion proposed recently is extended to 3D conditions for fatigue prediction. The influence of stochastic impact position is considered by statistical analysis. After analysis, the formation of the serious unstable crack (continuous bites) on the switch blade can be revealed. From the perspective of service life, increasing traction coefficient and decreasing friction coefficient between wheel flange and switch blade gauge surface are beneficial but not significant. However, a speed increase from 36 to 54 km/h can lead to 40% reduction in service life. This work enhances the cognition of damage mechanism on switch blade and provides theoretical foundation for service life design and maintenance operation.     

全地形移动机器人车身结构分析与优化

为了提高全地形移动机器人车身结构的力学性能,提出了一种结合多体动力学、有限元分析与正交试验的优化方法。针对全地形移动机器人的满载弯曲和扭转工况,利用多体动力学分析获得了该移动机器人车身在运动中所受的外部载荷,并结合有限元分析获得了车身结构的动态力学性能参数,以验证极限工况下车身结构的力学性能。基于四因素三水平正交试验,研究了底板厚度、悬架支座厚度、悬架支座加强筋长度和增高支柱加强筋厚度对全地形移动机器人车身最大应力、最大变形量和质量的影响。利用灰色关联分析法对正交试验结果进行分析。通过对比各因素的灰色关联度获得了全地形移动机器人车身结构的最佳优化方案：底板厚度为5 mm、悬架支座厚度为2 mm、悬架支座加强筋长度为65 mm和增高支柱增设2 mm厚加强筋。分析结果表明,相较于原始方案,优化后全地形移动机器人车身在质量减小6.93%的同时,最大应力减小了12.47%,最大变形量减小了41.69%,说明该优化方案可在提高车身结构性能的同时减小车身质量和降低整车功耗,验证了所提出的优化方法的有效性。研究结果可为机械结构的动态力学性能分析与优化提供参考。     

Two-way bending behavior of 3-D GFRP sandwich panels with through-thickness fiber insertions

This paper presents the details of a research program that was conducted to evaluate the two-way bending behavior of 3-D glass fiber reinforced polymer (GFRP) sandwich panels. The panels consist of GFRP skins with a foam core and through-thickness fiber insertions. While the behavior of these panels under one-way bending is relatively well understood the behavior under two-way bending has not yet been investigated. An experimental program was conducted to evaluate the effect of the fiber insertion pattern and the panel thickness on the two-way bending behavior under the effect of a concentrated load. The experimental results were used to verify a non-linear, static finite element model which was used to introduce a simplified method to predict the behavior. The measured and predicted responses indicate that at lower deflections the panel behavior is dominated by plate bending action while for higher deflections membrane action dominates. The finite element analysis was extended to study the effect of different parameters which were not tested in the experimental program. The parametric study indicates that increasing the relative flexural or shear rigidities of the panel alters the behavior towards the plate bending mechanism thereby reducing the percentage of load carried by membrane action.     

Effects of plate thickness on fatigue fracture behaviors of an aluminum alloy (Al‐Cu‐Mg)

High cycle fatigue properties of 2124 aluminum alloy plates with different thickness were investigated by determining fatigue S?N curves, fatigue crack growth rates and fracture toughness of 2124‐T851 aluminum alloy plates with the thickness of 30 mm, 40 mm and 55 mm, respectively. Fatigue fracture behaviors of alloy plates were also analyzed and discussed using scanning electron microscope morphology observation, energy spectrum analysis, X‐ray diffraction phase analysis and transmission electron microscopy observation in this paper. The results indicate that plate thickness affects the comprehensive fatigue properties of 2124 aluminum alloy plates. Thinner plate achieves better comprehensive fatigue properties. Due to the different amount of deformation during hot rolling, the variation of microstructure of alloy plates with different thickness mainly concentrates on the difference of grain sizes, substructure and volume fraction of grain boundaries. The thinner the plate, the smaller the grain sizes and therefore the thinner plate produces a higher volume fraction of grain boundaries and substructure, and a greater resistance to fatigue crack growth, thus thinner plate exhibits better fatigue properties.     

Evaluation of equi-biaxial fatigue of stainless steel by the pressurized disc fatigue test

The pressurized disc fatigue (PDF) test technique was employed to obtain fatigue lives of Type 316 stainless steel under equi-biaxial stress conditions. In the PDF test, a disc-type specimen was subjected to the cyclic bulge test. The biaxial fatigue lives were successfully obtained by the PDF tests, and they were longer than those obtained by the uni-axial and plate bending fatigue tests under the same equivalent strain range. Observations of crack initiation and growth behavior during the PDF test revealed that the relatively large size of the disc-type specimens had only a minor influence on the fatigue lives. Finite element analysis results showed the PDF test was valid for evaluating the fatigue lives under equi-biaxial conditions. It was concluded that the influence of equi-biaxial condition was not necessary to be considered in the design fatigue curve.